The present invention is directed to an automatically controlled signal translating system, such as an audio amplifier for a sound reinforcement system, that utilizes relatively inexpensive microprocessor techniques to control the gain of the signal translating system on a frequency selective basis to suppress positive feedback induced oscillation and/or to equalize the bandwidth response of the system. While described in connection with a sound reinforcement system, it will become apparent that the invention has use in other signal translating systems in which feedback would occur or in which nonuniform bandwidth response is a problem
It is well known that sound reinforcement systems typically suffer from instability due to acoustical feedback of the amplified sound through the microphone input. Changes in sound absorption of materials in the surrounding environment and movement of the microphone can have an adverse effect on stability of the sound reinforcement system even if no initial instability is encountered. The method most often used to control the occurrence of acoustic feedback is to smooth room response with an equalizer circuit usually inserted between the microphone and the power amplifier. By appropriate adjustment of the equalizer across the frequency spectrum, a smooth response characteristic can be achieved that minimizes the potential for oscillations to occur at any frequency in the spectrum. However, as noted, transient changes in the environment, such as movement of spectators or movement of the microphone, can disrupt the response characteristic and cause oscillations unless the equalizer is constantly attended to compensate for the changes.
While attempts have been made to provide systems that will automatically suppress feedback induced oscillations in systems of the type described, they have generally proven to be ineffective for the purpose or, in the case of computer based systems, to require high powered, costly computers to operate effectively which makes such systems impractical for commerical applications.
It is therefore an object of the present invention to provide an economical and effective oscillation suppressor and automatic equalizer for a signal translating system, such as a sound reinforcement system, that is effective to detect and suppress oscillations before they reach the stage at which they become irritatingly noticeable and, in most cases, before they become audible at all.